SULPHUR IN HIGH-TEMPERATURE NATURAL PROCESSES

Free sulphur can be generated and exist practically on the whole way of movement of magmatic gases by means of the chemical reaction H₂S+SO₂®H₂O+S. Additional quantity of free sulphur can arrive from mantle sources. As its critical temperature of 1040°C is in the temperature interval of possible magma existence, there should exist a zone or a system of segregation zones of liquid sulphur on the way of gas movement. The bottom border of each zone is determined by isothermal surface of 1040°C on the depths exceeding 700 m. The upper border of each zone is determined either by isothermal surface of repeated increasing of temperature over 1040°C or by isobaric surface (for the uppermost zone), concrete position of which depends on magma temperature (for 900°C - 450-550 m). Magma exudes large volumes of high-temperature water vapor before and during eruption. The appearance of considerable amounts of sulphur family gases is determined by the influence of high-temperature water vapor of water onto sulphur segregation zones. The vapor transforms sulphur from liquid state to gaseous and moves an equilibrium in the direction of role increase of sulphur family gases: H₂O+S®H₂S+SO₂. Free sulphur is transformed into liquid state again during cooling of substance in the magmatic channel after eruption. At the same time water vapor goes faster away out of magmatic rocks. At the expense of this the equilibrium is displaced in the opposite direction: H₂S+SO₂®H₂O­+S¯. It determines progressive lowering of relative amount of sulphur family gases. The high sorptive ability of sulphur allows to suggest the concept of "sulphuric interception", in which the main role in sulphide ore-forming processes belongs to high-temperature segregation zones of liquid sulphur. Metals interception and their accumulation take place inside zones of liquid sulphur. Pure sulphide melt is being formed from sulphur-sulphide liquid by thermal separation (sulphur's removing out of melt under the influence of increasing temperature).